Light coming through windows is best done with spotlights - this needs patience and lots of test renders, unfortunately. If you turn off shadows for the roof, you will most likely get an unrealistic band of light where it shines over the top of the walls; unless you can make the walls very tall with a morph, or perhaps by blocking the light with an additional prop. If you want interior lights as well, they will have to be spotlights too. I'd suggest getting the outside light to interact with the window first, though; and take care that your interior lights don't overpower it.